diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5a1ee70af90..26cccb45faf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -104,7 +104,7 @@ include(GNUInstallDirs)
 
 pkg_check_modules(SYSTEMD systemd)
 
-if(SYSTEMD_FOUND)
+if(SYSTEMD_FOUND AND (NOT DEFINED INSTALL_SYSTEMD_UNIT OR INSTALL_SYSTEMD_UNIT))
     pkg_get_variable(OTBR_SYSTEMD_UNIT_DIR systemd systemdsystemunitdir)
 endif()